Atmosphere
The earth’s atmosphere is a blanket of gases around the Earth. The proportion of gases changes in the higher layers of the atmosphere. Oxygen is negligible at the height of 120 km; carbon dioxide and water vapour are found only up to 90 km from the surface of the earth.
The atmosphere is composed of several layers, each with distinct characteristics and functions. These layers are:
Troposphere: It extends from the Earth’s surface up to about 8-15 km (5-9 miles) depending on latitude (higher at the equator, lower at the poles).
a) It contains approximately 75% of the atmosphere’s mass and 99% of its water vapour.
b) The temperature decreases with altitude.
c) Weather phenomena like clouds, rain, and storms occur in this layer.
d) It’s where we live and breathe, with air becoming thinner as altitude increases.
e) Its top most part is known as tropopause.
Stratosphere: It extends from the top of the tropopause (about 8-15 km) up to 50 km.
The ozone layer, which absorbs and scatters ultraviolet solar radiation, is found here, primarily from 15-35 km (9-22 miles).
a) Temperature increases with altitude due to the absorption of UV radiation by ozone.
b) This layer is more stable and less turbulent, making it ideal for jet aircraft travel.
Mesosphere: Its extension is from about 50 to 80 km.
a) Temperature decreases with altitude, making it the coldest layer of the atmosphere.
b) It is where most meteorites burn up upon entering the Earth’s atmosphere.
c) The upper limit of mesosphere is known as Mesopause.
Thermosphere: It is from about 80 to 400 km above mesopause.
a) Temperature increases significantly with altitude, potentially reaching up to 2,500°C (4,500°F) or more. But we cannot feel while reaching here as the movement of air is nil.
b) It contains a small fraction of the atmosphere’s mass but is crucial for absorbing high-energy X-rays and UV radiation from the sun.
c) The thermosphere is where the auroras occur and where the International Space Station orbits.
The lower part of thermosphere is Ionosphere. It is ionized by solar radiation, creating free electrons and ions.
a) It plays a crucial role in radio communication by reflecting and refracting radio waves back to the Earth.
b) The ionosphere is also responsible for the auroras and helps protect the Earth from harmful solar and cosmic radiation.
Exosphere
The layer above ionosphere is exosphere.
a) This is the outermost layer, gradually transitioning into the vacuum of space.
b) The air is extremely thin, with particles so sparse they can travel hundreds of km without colliding.
c) Satellites orbit in this layer due to the minimal air resistance.
Understanding these layers helps us grasp how our planet’s climate and weather systems function, how they protect life, and how they interact with. The atmosphere plays a crucial role in shaping Earth’s climate through several key processes.
Some other factors that affect climate:
- Regulation of Temperature
Greenhouse Effect: The atmosphere contains greenhouse gases (GHGs) like carbon dioxide (CO₂), methane (CH₄), and water vapour. These gases trap heat from the Sun in the atmosphere, preventing it from escaping back into space. This natural greenhouse effect keeps Earth’s surface warm enough to support life. Without it, our planet would be an inhospitable ice ball. Hence the atmosphere acts as a thermal blanket, reducing the temperature extremes between day and night. This insolation helps maintain relatively stable temperatures conducive to life.
- Distribution of Heat
Atmospheric Circulation: The atmosphere distributes heat from the equator, where sunlight is most intense, to the poles. This transfer occurs through wind patterns and ocean currents, creating diverse climates around the world. For instance, the Hadley cells, Ferrel cells, and Polar cells are large-scale circulation patterns that redistribute warm and cold air across the globe.
Ocean-Atmosphere Interaction: The atmosphere and oceans interact closely. The wind drives ocean currents, which transport heat across the planet. Phenomena like El Niño and La Niña result from these interactions, significantly influencing weather patterns globally.
- Water Cycle
Evaporation and Condensation: The atmosphere is integral to the water cycle. It facilitates the evaporation of water from oceans, lakes, and rivers, and it transport through the air as water vapour. This vapour eventually cools and condenses to form clouds, leading to precipitation (rain, snow, etc.). This cycle is crucial for distributing fresh water across the planet.
Clouds and Albedo: Clouds, formed from condensed water vapour, play a dual role. They reflect some of the incoming solar radiation back into space (albedo effect); cooling the planet, while also trapping heat, contributing to the greenhouse effect.
- Influence on Weather Patterns
Weather Systems: The atmosphere’s dynamics create weather systems like cyclones, anticyclones, and fronts. These systems govern daily weather and are influenced by the complex interactions of temperature, pressure, and humidity in the atmosphere.
Storms and Extremes: The atmosphere is responsible for the formation of storms, including thunderstorms, hurricanes, and tornadoes. These extreme weather events significantly impact climate and can cause severe damage.
- Chemical Composition and Climate Change
Human Impact: Human activities, such as burning fossil fuels and deforestation, have altered the chemical composition of the atmosphere, increasing concentrations of GHGs. This enhancement of the greenhouse effect leads to global warming and changes in climate patterns.
Aerosols and Pollutants: Aerosols (tiny particles in the atmosphere) from natural and anthropogenic sources can cool the planet by reflecting sunlight or contribute to warming by absorbing heat. They also affect cloud formation and precipitation.
- Protection from Harmful Solar Radiation
Ozone Layer: The stratospheric ozone layer absorbs and scatters the majority of the Sun’s harmful ultraviolet (UV) radiation. This protection is vital for life on Earth, preventing harmful effects like skin cancer and cataracts in humans and damage to ecosystems.
- Feedback Mechanisms
Climate Feedbacks: The atmosphere interacts with Earth’s surface in feedback loops. For example, as polar ice melts, less sunlight is reflected away (lower albedo), leading to more absorption of heat and further warming. Similarly, warming can increase water vapour in the atmosphere, a potent GHG, amplifying the greenhouse effect.
Conclusion
In summary, the atmosphere is not just a passive layer of gases; it is a dynamic system that regulates and moderates Earth’s climate. Its interactions with solar radiation, surface features, and human activities intricately weave the fabric of our climate system, influencing everything from daily weather to long-term climate trends. Understanding these processes is crucial for addressing the challenges of climate change and ensuring a sustainable future for our planet.